The document discusses engineering challenges for future wind energy development. It outlines goals of providing 20% of US electricity from wind by 2030, but barriers like transmission, resource assessment accuracy, and turbine response to turbulence must be overcome. Key challenges are understanding turbulence's impact on turbine loads, collaborating with meteorologists on wind forecasts, and developing offshore wind platforms and solutions for the complex offshore environment. Success will require a multidisciplinary approach across engineering and atmospheric science.

1. ENGINEERING CHALLENGES FOR
FUTURE WIND ENERGY
DEVELOPMENT
Neil D. Kelley
National Wind Technology Center
11th H.T. Person Homecoming Lecture in Engineering
University of Wyoming
October 13, 2006

2. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 2
We Will Be Discussing . . .
• What has been accomplished in wind energy technology
to date?
• What are the future goals?
• What are current barriers to meeting those goals?
• What are the engineering challenges that will need to be
surmounted in order to overcome these barriers?
• The need for a multi-disciplinary approach to carry out
those challenges.

3. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 3
Where the Wind Is In the United States

4. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 4
What has been accomplished in wind
energy technology to date?

5. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 5

6. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 6
There are a Range of Wind Turbine Sizes and Applications
Small (≤10 kW)
• Homes (Grid
connected)
• Farms
• Remote Applications
(e.g. battery changing,
water pumping, telecom
sites, icemaking)
Intermediate
(10-500 kW)
• Village Power
• Hybrid Systems
• Distributed Power
Large (500 kW – 6 MW)
• Central Station Wind Farms
• Distributed Power
• Offshore Wind Generation
Stations

7. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 7
Growth of Wind Energy Capacity Worldwide
0
10000
20000
30000
40000
50000
60000
70000
90 91 92 93 94 95 96 97 98 99 '00 '01 '02 '03 '04 '05 '06 '07 '08
Rest of World
Actual Projected
Rest of World
North America North America
Europe Europe
Jan 2006 Cumulative MW = 56,813
Rest of World = 7,270
North America = 9,550
Europe = 39,993
Sources: BTM Consult Aps, Sept 2005
Windpower Monthly, January 2006

8. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 8
2012 Goal :
3.6 cents/kWh
with no PTC#
Cost of Energy Trend
1981: 40 cents/kWh
Decreasing Cost Due to:
• Increased Turbine Size
• R&D Advances
• Manufacturing improvements
NSP 107 MW Lake Benton, MN wind farm
2006: 5-8 cents/kWh with no PTC#
Cost Increases Due to:
• Price increases in Steel & Copper
• Turbines Sold Out for 2 Years
#Federal production tax credit

9. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 9
How has this been accomplished?

10. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 10
The Wind Turbine Designer’s Toolbox: The NWTC
Suite of Advanced Numerical Simulation Codes
Measurements
(power, loads, accel., wind)
Aerodynamics
(AeroDyn)
Structural
Dynamics
(FAST, ADAMS)
Controls
(user-defined)
Wind Field
(TurbSim, field
exp., etc.)
Actuator Inputs
(blade pitch, gen. torque, yaw)
Aerodynamic Loads
(lift, drag, pitch mom.)
Blade Motions
(blade pitch, element pos. & vel.)
Wind-Inflow
Time Series Loads
(forces, moments)
Time Series Motions
(defl., vel., accel.)
Output
Other
External
Conditions External Loads
(earthquake, wave)
Platform Motions
(defl., vel., accel.)

11. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 11
The Development of
New Testing Facilities
A new 45-meter wind turbine blade
design being tested in the NWTC Blade
Test Facility
Latest blades are now reaching 61.5 m
lengths for 5 MW size turbines.

12. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 12
Tools for Developing
Advanced Generators and
Drive Trains
GEC
NPS
Today
1.5 MW Commercial Technology
Tomorrow
Prototype Technology
NWTC 2.5 MW Dynamometer Facility

13. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 13
Meet the Need for Understanding Available
Materials and Developing New Ones

14. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 14
Future Goal: Provide 20% of U.S. Electrical
Energy from Wind by the Year 2030
 Increasing the reliability and service lifetime of wind turbine
components and systems (risk reduction)
 Improving both the power quality and consistency to increase
the net worth of wind-generated electricity
 Reducing the cost of wind turbine operations and maintenance
 Removing technical barriers/issues
Achieve This Through Market Transformation
by . . .

15. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 15
What Are the Barriers To Meeting These
Goals?
• Adequate transmission to connect wind resource regions
with load centers
• The current level of intermittency and the accuracy of wind
forecasts
• The accuracy of the initial resource assessment and the lack
of site-specific characteristics in those assessments that
may affect the operation and lifetime of the installed turbines
• Interference with ground-based RADAR and other military
and civilian communications and navigational systems
• Environmental impacts such as avian interactions, noise,
esthetics

16. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 16
Advanced Wind Turbine Component Design
Studies
WindPACT: Wind Partnership for Advanced Component Technologies
Blades
Drive Trains
Towers

17. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 17
Where is the Wind Resource Located That
Will Provide the Needed Power to Feed the
Primary U.S. Load Centers?
• Onshore
• Offshore

18. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 18
onshore and offshore
Source of Wind Energy for 20% Scenario

19. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 19
U.S. Rational to Pursue Offshore Wind
Energy Development
US Population Concentration
US Wind Resource
Graphic Credit: GE Energy
% of with Class 3 winds or above
• Windy onshore sites are not close to population centers
• The electric utility grid cannot be easily set up for interstate transmission
• Load centers are close to offshore sites

20. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 20
Region 0 - 30 30 - 60 60 - 900 > 900
New England 10.3 43.5 130.6 0.0
Mid-Atlantic 64.3 126.2 45.3 30.0
Great Lakes 15.5 11.6 193.6 0.0
California 0.0 0.3 47.8 168.0
Pacific Northwest 0.0 1.6 100.4 68.2
Total 90.1 183.2 517.7 266.2
GW by Depth (m)
U.S. Offshore Resource
Southeast and Gulf Coasts
have not been evaluated

21. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 21
What Are The Engineering Challenges
Necessary To Overcome These Barriers?
• Develop engineering solutions and methodologies that utilize
new materials, structures, and controls to accommodate a
wide range of turbine operating environments
• Understanding the detailed role of atmospheric motions in
the aeroelastic response of wind turbine structures and its
long-term consequences
• Collaborate with the atmospheric science community in the
development of new tools to predict not only future wind farm
power output over a period of 24-48 hours in advance but
conditions that may have a deleterious impact on turbine
operations

22. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 22
Coming to Grips with Turbulence Within the
Atmospheric Boundary Layer and Its Impact
on the Dynamic Response of Wind Turbines
• Wind turbines experience the greatest numbers of fatigue
cycles of any man-made structure within their lifetime
• The source of these cycles is primarily atmospheric
turbulence

23. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 23
Multi-Megawatt
Capacity Wind
Turbines Are
Huge Structures
Boeing 747-400
GE 3.6 MW Turbine
Designed for Offshore Use
104-m Rotor Diameter

24. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 24
A Ubiquitous Structure in the Nighttime Atmospheric
Boundary Layer: The Low-Level Jet Stream
Eventual
Max
Turbine
Depth
p
4 6 8 10 12 14 16 18 20 22
Height(m)
0
100
200
300
400
500
Typical Vertical Wind
Profiles Associated
With Low-Level Jets
Lamar, Colorado
Low-Level Jet
10-min mean wind speed (m/s)
Strong Correlation Between Wind
Resource and Jet Bi-annual Frequency
After Bonner, 1968

25. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 25
Source: R. Banta, NOAA/ESRL
Horizontal distance (km)
Height(km)
waves
low-level
jet
organized
turbulent air
motions from
waves
height of
wind speed
maximum
high vertical
shear
region
LIDAR Observation of Wave Motions in
Southern Kansas
Low-Level Jets Are Responsible for the Generation of Organized
or Coherent Turbulence by Atmospheric Wave Motions
SCHEMATIC OF COHERENT
TURBULENCE GENERATION

26. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 26
LIDAR Observation of Low-Level Jet and Spatial
Distribution of Turbulence in Southeast Colorado
20:16 to 21:12 LST 23:11 to 23:29 LST15 September 2003
Jet
Maxima
Organized
Turbulent
Region Turbine
Rotors

27. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 27
Role of Jets and Turbine Structural Loads
Intense vertical shear
and stable flow beneath
the low-level jet provides
the catalyst for developing
atmospheric wave motions
Breaking
atmospheric
wave motions
produce bursts
of coherent
turbulence
Transient loads
are induced when
turbine rotors
encounter
coherent
turbulent
regions

28. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 28
0
100
200
300
400
500
600
700
12 AM 4 AM 8 AM 12 PM 4 PM 8 PM 12 AM
Time
FaultTime(hours)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
WindShearExponent
Fault Time
Shear
Diurnal Variation in Turbine Fault and Vertical Wind
Shear Patterns Observed at Big Spring, Texas
Number of
Hours
With
Turbines In
Fault Status
Vertical
Wind
Shear
Source: Global Energy Concepts
Turbines Tend to Develop Fault Conditions
More Often at Night. Why?
peak low-
level jet
activity

29. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 29
The Need for Close Collaboration Between
the Engineering and Atmospheric Science
Communities
• Atmospheric dynamics clearly have a significant impact on
wind turbine operations and longevity beyond just the
amount of wind energy available for power production
• It is likely that turbine load reduction will require a more
detailed knowledge of turbulent atmospheric structures and
mitigation approaches that include real-time atmospheric
measurements in the control scheme
• The future ability to utilize operational weather forecast
models to warn of potentially harmful events as well as
predicting future power production will contribute to
increased wind farm productivity and efficiency

30. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 30
An Example of Collaborative Synergism
Development of a Low-
Dimensional Wind Turbine
Inflow Model
William Lindberg
Jonathan Naughton
Department of Mechanical Engineering
Thomas Parish
Robert Kelly
Department of Atmospheric Science
John Spitler
Department of Mathematics
Simulated detailed turbine inflow
Low-dimensional reconstruction

31. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 31
The Engineering Challenge of Building Wind
Farms Offshore
•Platforms
•The Operating Environment

32. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 32
The Development of Turbine Platforms for Deep
Water Installations
Current Technology

33. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 33
The Deep Water Operating Environment:
A Major Engineering Challenge
Turbulent winds
Irregular waves
Gravity / inertia
Aerodynamics:
 induction
 skewed wake
 dynamic stall
Hydrodynamics:
 scattering
 radiation
 hydrostatics
Elasticity
Mooring dynamics
Control system
Fully coupled

34. October 13, 2006 N.Kelley --- H.T. Person Homecoming Lecture 34
Conclusions
• A tremendous opportunity exists for engineers trained in a
range of disciplines to contribute to the development of a
mature wind energy industry poised to meet the 2030 goal.
• The same holds true for meteorologists who wish to work in
numerical forecasting and those who enjoy problem solving
and working with engineers toward a common goal.
• Future progress on overcoming the barriers discussed and
improving the reliability and worth of wind-generated
electricity will depend on the extent these problems are
approached using a multi-disciplinary, synergistic
methodology.